This present invention relates to improvements in projected light plumb devices which are generally utilized to vertically align a floor position with a corresponding ceiling position or vice versa in which a light projecting device is buoyantly supported within a fluid filled container. The light projecting device is mounted on a float platform which is horizontally supported by the floor in such a manner that regardless of the floor's inclination, the light projecting device will transmit a beam of light along a vertical line.
Such a device is disclosed in my prior patent U.S. Pat. No. 5,184,406 issued Feb. 9, 1993. The device therein is comprised of essentially three elements: a container retaining a quantity of the suspension fluid such as water, oil or the like, a float platform buoyantly supported by the fluid within the container, and a light projecting device mounted on the float platform in a manner so that the light projecting device will transmit a beam of light in a vertical line. In addition, the device has a support tube to allow the light projecting device to be selectively mounted on the platform.
The disclosure of my prior patent U.S. Pat. No. 5,184,406 is incorporated herein by reference.
The present invention is directed to improvements in the support platform, and the provision of a locator plate to allow the facile alignment of the device on a base or floor surface.
In my prior patent, the container had alignment markers formed in quadrants on the outside surfaces of the walls of the container.
In utilizing the device according to my prior patent, the support surface or floor was marked with perpendicular square lines to indicate at their intersection the point on the floor on which is desired to line up the upper ceiling point with the quadrant markings on the outer walls of the container aligned with these markings on the floor. This required sighting views and the alignment was easily subject to parallax error if the user was not careful. Furthermore, when the reverse procedure was followed; i.e. picking a point on the ceiling and marking a point on the floor directly below, the device would be moved to align with the point in the ceiling and four hatch marks were required to be made on the floor and then draw cross lines in order to mark the point on the floor directly below the point on the ceiling. This was somewhat time consuming and, as indicated subject to sighting or parallax errors and required a fair degree of care in carrying out the procedure.
In using the prior model of the device in U.S. Pat. No. 5,184,406, it has been found with the substantially flat lower surface of the float platform and the uninterrupted lower surface that when the device had recently been moved about that there was some tendency of air bubbles to form in the buoyant fluid adjacent the lower surface of the float platform. Such air bubbles were often distributed nonuniformily and could cause the introduction of minor errors in the absolute levelness of the float platform as one portion of the platform floated higher or lower than the other.